1. Field of the Invention
The present invention relates to a method for repairing a tubular conduit by lining the inner wall of the tubular conduit with a tubular liner bag.
2. Description of the Prior Art
When an underground tubular conduit, such as pipelines and passageways, becomes defective or too old to perform reliably, the tubular conduit is repaired and rehabilitated without digging the earth to expose the tubular conduit and disassembling the sections of the tubular conduit. This non-digging method of repairing an underground conduit has been known and practiced commonly in the field of civil engineering. Typically, the method is disclosed by Japanese Provisional Patent Publication (Kokai) Sho 60-242038.
According to this publication, this method of conduit repair comprises inserting a sufficiently long tubular flexible liner bag into the tubular conduit to be repaired by means of a pressurized fluid, like air and water. The tubular liner bag is made of a flexible resin-absorbent material impregnated with a thermosetting liquid resin, and has the outer surface covered with an impermeable plastic film.
More particularly, according to the publication, the tubular flexible liner bag is closed at one end and open at the other; the tubular flexible liner bag is first flattened, then, the closed end of the tubular liner bag is tied to a control rope; the open end of the tubular liner bag is made to gape wide and hooked (anchored) at the end of the defective or old tubular conduit in a manner such that the wide-opened end of the liner completely and fixedly covers and closes the conduit end; a portion of the liner is pushed into the conduit; then, the pressurized fluid is applied to the said portion of the tubular liner such that the fluid urges the tubular liner to enter the conduit. Since one end of the tubular liner is hooked at the end of the conduit, it remains there while the rest of the flexible liner bag is turned inside out as it proceeds deeper in the conduit, and this manner of insertion is exactly what is meant by the term "everting" as used above and it shall mean so throughout this application document. When the entire length of the tubular liner bag is everted (i.e., turned inside out) into the conduit, the control rope holds the closed end of the tubular liner bag to thereby control the length of the tubular liner in the conduit. Then, the everted tubular liner is pressed against the inner wall of the conduit by the said pressurized fluid, and the tubular flexible liner is hardened as the thermosetting liquid resin impregnated in the liner is heated, which is effected by heating the fluid filling the tubular liner bag by means of a hot steam, etc. It is thus possible to line the inside wall of the defective or old conduit with a rigid liner without digging the ground and disassembling the conduit sections.
However, in this conventional method, when the fluid used is a liquid such as water, it is necessary to heat the entire body of the liquid contained in the reversed tubular liner bag, and this consumes a considerable amount of fuel or electricity as well as time, especially when the diameter or the length of the conduit to be repaired is large. Also, since this conventional method uses a large volume of the liquid, it requires a large-sized boiler, hot water pump, heating and circulation installation, etc. Thus, the preparation as well as the operation for the conduit repair takes many hours and large cost. Consequently, with this conventional heating method, the operation efficiency is poor and the operation cost is high.
In order to overcome this problem, one of the present inventors contrived an improved method for repairing a tubular conduit, which is described in a patent application of U.S. Ser. No. 07/776,046 and will be explained briefly as follows, with reference to FIG. 3. Thus, according to this formerly proposed invention, an everted tubular liner bag 102 impregnated with a thermosetting liquid resin was inflated inside a tubular conduit 101 by means of air pressure to fit closely to the inner wall of the conduit 101; then, a heat-resistive sprinkler hose 107 which had been inserted in the tubular liner bag 102 was supplied with hot water so that the hot water was sprinkled onto the tubular liner bag 102 to thereby harden the thermosetting resin impregnated therein. Thus, in this proposed method, the tubular liner bag 102 pressed against the inner wall of the conduit 101 was uniformly heated by the hot water sprinkled on it by the sprinkler hose 107 whereby the thermosetting resin impregnated in the tubular liner bag was caused to uniformly harden, so that the heat energy required was only that used to heat up the water for sprinkling and not the bulky volume of the water that would have filled the tubular liner bag 102 in the case of the conventional method, and since the volume of the water used was much smaller, the boiler 122, the hot water pump 121, and other heating and circulation devices could be ones of small sizes and low capacities, and the repair of the conduit 101 could be accomplished in a relatively short time and at a reduced cost even when the conduit 101 had a large diameter or a large length.
(Problems the Invention seeks to solve)
Now, in the above improved method, the sprinkler hose 107 was directly fastened to one of guide tubes 105, which were formed integrally with a lid member 103b of an anchor frame 103, as shown in FIG. 3, so that the length of the sprinkler hose inside the tubular liner bag 102 was not controllable. Therefore, it was necessary to predetermine the length of the sprinkler hose 107 in precise relation to the length of the tubular conduit 101, because when the sprinkler hose 107 was too long, it could be sucked by a suction hose 109 and plug the latter, or it could bend acutely to stop the flow of the hot water therein whereby the proper sprinkling would not occur. On the other hand, when the sprinkler hose 107 was too short, the head portion of the tubular liner bag 102 could not be sprinkled with hot water. However, it was in practice impossible to measure the length of an underground conduit with high precision, and furthermore, the sprinkler hose 107 would necessarily expand and its length would increase when hot water was passed in it. Therefore, it was very difficult to predetermine the optimum length of the sprinkler hose 107 to be used, and in most instances, the length is selected to be greater than an apparently sufficient value to be on the safer side. Also, with the conventional methods, it was necessary to tailor-make a sprinkler hose 107 of a suitable length each time a conduit 101 of a different length was repaired, and this was very uneconomical.
The present invention was contrived in view of the above problems, and it is, therefore, an object of the invention to provide a new method for repairing a tubular conduit which method is so contrived that the length of the sprinkler hose inside the tubular liner bag can be controlled to an optimum value such that a proper sprinkling of hot water occurs throughout the length of the tubular liner bag so that the repair work becomes more economical and effective.